Introducción terminológica: gentilicios y toponimia

The estimated mean negative binomial distribution for each state of hidden Markov model, including species ratio TTCh as a covariate, are presented in Appendix 4.19. For call rate, judging by the mean values, states 1 to 3 were labelled as low, medium and high call rate, respectively. Two additional states were added for mean frequency, with states 1 to 5 labelled as very low, low, medium, high, and very high, respectively.

Species ratio TTCh was categorised as low ratio (≤ 33 % oceanic bottlenose dolphin), state 2 as medium ratio (≥ 34 – ≤ 67 % oceanic bottlenose dolphin), and state 3 as high ratio (≥ 68 % oceanic bottlenose dolphin), based on the ratio of animals in the frame. The stationary distribution of call rate (Figure 4.4A) and mean frequency (Figure 4.4B) were then considered. For call rate, moving from oceanic bottlenose dolphin only to low ratio groupings, the probability of being in the fewest calls sate decreased steadily.

The use of states with a moderate or high number of calls, respectively, gradually increased (Figure 4.4A). Indeed, the probability of being in state 1 (lowest call rate) was 37.1 % when oceanic bottlenose dolphins only were present. The addition of a few pilot whales in the group increased the call rate to 50.2 % (oceanic bottlenose dolphin high ratio) before it decreased when the ratio of oceanic bottlenose dolphin to pilot whale was lower (Figure 4.4A).

In the case of mean frequency, when moving from oceanic bottlenose dolphin only to oceanic bottlenose dolphin low species ratio, the probability of being in a higher mean frequency state (states 4 and 5) increased when any pilot whales were present, while the probabilities of low frequency vocalisation (states 1, 2 and 3) occurring gradually decreased once pilot whales were present (Figure 4.4B). While the probability of being in state 1 was 57.2 % in the presence of only oceanic bottlenose dolphins (e.g., oceanic bottlenose dolphin only), it decreased by 98.3 % (down to approximately 1.0 %) when ≤ 33 % of the group were oceanic bottlenose dolphins.

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Figure 4.4: Stationary distributions for different values of species ratio TTCh and A) call rate and B)

mean call frequency of oceanic common bottlenose dolphins (T. truncatus). Note, OBDO = groups with oceanic bottlenose dolphins only, OBD high = groups with high ratio oceanic bottlenose dolphin to pilot whale (Globicephala sp.)they are in association with, OBD medium = groups with medium ratio oceanic bottlenose dolphin to pilot whale they are in association with, OBD low = groups with low ratio oceanic bottlenose dolphin to pilot whale they are in association with.

The transition rates between states are shown in Figure 4.5. For call rates, when oceanic bottlenose dolphins were in the low-call rate (state 1), the between-state transition probabilities hardly changed as oceanic bottlenose dolphin ratio changed (Figure 4.5). Conversely, the probability of switching from state 2 to state 1 and 2 to 3 appeared to be heavily influenced by oceanic bottlenose dolphin ratio. In particular, when transitioning from 2-1 it steadily increased to 45.2 % as the ratio of oceanic bottlenose dolphins decreased. When transitioning from state 2 – 3, probability takes a relatively high value (22.1 %) when oceanic bottlenose dolphins were with a small number of pilot whales. Probability dramatically dropped when the dolphins were in groups with a medium (down to 6.1 %) or low ratio (down to 4.3 %) compared to pilot whales. Overall, the oceanic bottlenose dolphins were more likely to leave the low-call-rate state when they were with pilot whales and leave the high-call-rate state when they were with a proportionally larger number of pilot whales. Additionally, they were more likely to remain in this comparatively silent state when proportionally more pilot whales were present.

Chapter 4 – Signal exchange of oceanic common bottlenose dolphin (Tursiops truncatus) during intra- and inter-species associations in Far North waters, New Zealand

Figure 4.5: Between-state transition probabilities for different species ratio TTCh and call rate of oceanic common bottlenose dolphins (T. truncatus). Note, OBDO = groups with oceanic bottlenose dolphins only, OBD high = groups with high ratio oceanic bottlenose dolphin to pilot whale (Globicephala sp.) they are in association with, OBD medium = groups with medium ratio oceanic bottlenose dolphin to pilot whale they are in association with, OBD low = groups with low ratio oceanic bottlenose dolphin to pilot whale they are in association with.

Oceanic bottlenose dolphins were also more likely to leave the low-frequency state when they were in lower ratio to pilot whales and utilise the high and very high-frequency states when they were in low ratio. The rates of transition between states with species ratio TTCh as a covariate for mean frequency are given in Figure 4.6A & B. The between-state transition probabilities appeared to be heavily influenced by species ratio. In particular when transitioning from state 1, the highest value (34.0 %) was observed when the dolphins were in oceanic bottlenose dolphin medium groups, after steadily increasing from 22.4 % in oceanic bottlenose dolphin only groups. Overall, the dolphins were more likely to leave the low- frequency state (state 1) when they were in higher ratio to pilot whales (oceanic bottlenose dolphin only and oceanic bottlenose dolphin high) (Figure 4.6A) and used the high and very high-rate states (states 4 and 5) when they were in low ratio (oceanic bottlenose dolphin low; Figure 4.6B). 0.0 0.1 0.2 0.3 0.4 0.5

OBDO OBD high OBD medium OBD low

P roba bi li ty Species ratio 1-2 1-3 2-1 2-3 3-1 3-2

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Figure 4.6: Between-state transition probabilities for different species ratio TTCh and mean call frequency of oceanic common bottlenose dolphins (T. truncatus) Note, OBDO = groups with oceanic bottlenose dolphins only, OBD high = groups with high ratio oceanic bottlenose dolphin to pilot whale (Globicephala sp.) they are in association with, OBD medium = groups with medium ratio oceanic bottlenose dolphin to pilot whale they are in association with, OBD low = groups with low ratio oceanic bottlenose dolphin to pilot whale they are in association with. A) transitions from state 1 – 3 and B) transitions from state 4 – 5

No states showed high persistence, resulting in a pattern of shorter periods of each state. Transition from a low-call-rate (state 1) to a high-call-rate (state 3) state and vice versa often took place abruptly, rather than gradually via the medium-state. The decoding of call rate

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

OBDO OBD high OBD medium OBD low

P roba bi li ty 1-2 1-3 1-4 1-5 2-1 2-3 2-4 2-5 3-1 3-2 3-4 3-5 0.0 0.1 0.2 0.3 0.4 0.5 0.6

OBDO OBD high OBD medium OBD low

P roba bi li ty Species ratio 4-1 4-2 4-3 4-5 5-1 5-2 5-3 5-4 A B

Chapter 4 – Signal exchange of oceanic common bottlenose dolphin (Tursiops truncatus) during intra- and inter-species associations in Far North waters, New Zealand

indicated that the dolphins persisted 11.0 %, 41.3 %, and 16.2 % of the time for states 1, 2, and 3, respectively (Figure 4.7).

Figure 4.7: Transition matrix for three state model of call rate in the presence of varying species ratio TTCh of oceanic common bottlenose dolphins (T. truncatus). Note, State 1 = low call rate, State 2 = medium call rate and State 3 = high call rate. Key: Blue numbers = state, black number = transition rate, arrow direction = direction of transition between states.

The same pattern was apparent in mean frequency models (Figure 4.8), where dolphins also persisted in their mean frequency state 9.2 %, 18.2 %, 23.1 %, 23.5 %, and 12.7 % of the time in states 1, 2, 3, 4, and 5, respectively. Consequently, the dolphins appeared to stay in the state with medium vocalisation rate and frequency (states 3 and 4) compared to the states with low and high rates and frequency vocalisation (states 1, 2 and 5).

Figure 4.8: Transition matrix for five state model of mean call frequency in the presence of varying

species ratio TTCh of oceanic common bottlenose dolphins (T. truncatus). Note, State 1 = very low, State 2 = low, State 3 = medium, State 4 = high and State 5 = very high mean call frequency. Key: Blue numbers = state, black number = transition rate, arrow direction = direction of transition between states.

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